Projection technology is becoming wide spread thanks to rapid technology evolution and more efficient production techniques. Reference is made to the book “Projection Displays”, E. H. Strupp and M. H. Brennesholtz, Wiley, 1999.
Current commercially available projectors can only project one computer or data image in its native resolution if it is a high resolution image such as for example SVGA (Super VGA or Super Video Graphics Array or Adaptor, 800*600 pixels), XGA (Extended Graphics Array or Adaptor, 1024*768 pixels), 16:9 HDTV standard format (1280*720 pixels), SXGA (Super XGA, 1280*1024 pixels), Wide XGA (1365*768 pixels), SXGA+ (1400*1050 pixels), UXGA (Ultra XGA, 1600*1200 pixels), 16:9 HDTV standard format (1920*1080 pixels), 16:10 widescreen PC displays (1920*1200 pixels), 16:9 European HDTV format (2048*1152 pixels) or Quad XGA (2048*1536 pixels). Reference is made to the book “Display Interfaces”, R. L. Myers, Wiley, 2002, for explanation of these terms.
When it is desired to project multiple computer or data images on one screen in native resolution, e.g. images from two laptop computers in order to be able to compare them, then often one projector per displayed image is used. This solution is expensive because of the cost of supplementary projectors. Furthermore, it brings along additional problems, the most important of which are geometrical alignment of the different images and colour adjustment of these images projected by different projectors.
The geometrical alignment forms a problem because each projector has its own projection lens with its own geometrical aberrations or distortions. Projecting a plurality of such distorted images adjacent each other always involves some bad alignment, as represented for example in FIG. 1, which shows two images 2, 4 projected adjacent each other onto a projection surface 6 by two different projectors. Each of the images 2, 4 is distorted.
The book by Myers above proposes a hypothetical solution to the problem of displaying images of different resolution on a single display by means of conditional updating. That is each sub-image has to be updated separately rather than the complete screen as an entity.
When images of different projectors are combined, furthermore these images need to be colour adjusted so that originally colour matched images look the same, since the projected image of each projector has a slightly different colour point and colour uniformity. Even with the best possible known colour compensation schemes, one can always notice a visible difference. Because of colour drift of projectors over time, this difference can get bigger over time.
When a plurality of images are projected by means of a single projector, such as for example projection of high-resolution images adjacent each other as described in the parent application U.S. Ser. No. 10/330,943 of the present CIP, a selection of image sources of which the images are to be projected may need to be performed. No user-friendly way for doing this is currently available.
U.S. Pat. No. 6,493,008 describes a multi-screen display system and method which enables the simultaneous display of image data inputted from a plurality of image sources on a display unit, and which unifies the control relating to each image on a multi-screen. The multi-screen display system receives images from a plurality of image sources, and displays the received images at the same time on the multi-screen of a display device. In the multi-screen display system, a multi-screen control part determines a type of each image source and a display region where a multi-screen control cursor is positioned on the multi-screen. The multi-screen control part determines a role of the multi-screen control cursor in the display region according to the type of the image source of an image displayed in the display region where the multi-screen control cursor is positioned. The multi-screen control part controls generation of the multi-screen control cursor and the operation thereof so that the multi-screen control cursor can play the determined role. That system described works with a by a workstation generated on-screen display (OSD), which the user has to know. It is necessary to generate an additional OSD through the PC or workstation, on which then can be clicked, e.g. through a remote control, to change properties of the selected images. A broadcasted scenario is needed for generating the interaction means. It is known that OSDs are becoming increasingly complex, which may make it difficult for a user to select and handle a few of a plurality of input sources for combined display of images onto a single screen.
In projection devices for simultaneous projection of data from at least two input sources selected from a plurality of input sources, it is desirable to have a user-friendly selection capability, as often it is possible to connect a lot of computer, data and/or video sources (e.g., but not limited to, up to 20 different input sources), while only displaying a couple of them. In this case, a user-friendly method of selecting these different inputs is very important, in particular for ordinary, non-specialised user. At present, such user-friendly selection capability is not present.